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Thursday, 5 January 2017

The reproductive system of a child is not mature and
needs to change as a boy or girl develops into an adult, so that the system is
fully working. These changes begin between the ages of ten and fifteen. The
time when the changes happen is called puberty.

The changes happen because of sex hormones produced by
the testes in boys and by the ovaries in girls. Some changes happen in boys and
girls, while others just happen in boys or girls.

Here are some changes that happen to both boys and
girls:

underarm hair grows

pubic hair grows

body smell gets
stronger.

emotional changes

growth rate increases

The time when the physical changes and emotional
changes happen is called adolescence.

Boys

Here are some changes that happen only to boys:

voice breaks (gets deeper)

testes and penis get
bigger

testes start to produce sperm cells

shoulders get wider

hair grows on face and chest.

Girls

Here are some changes that happen only to girls:

breasts develop

ovaries start to release egg cells (periods start)

hips get wider.

The
female reproductive system

The female reproductive system contains these parts:

ovaries

Falopian tubes or egg tubes

uterus (pronounced "yoo-ter-russ")

cervix

vagina.

Ovaries

The two ovaries contain hundreds of undeveloped female
sex cells called egg cells or ova. Women have
these cells in their bodies from birth - whereas men produce new sperm
continually.

Fallopian tubes or egg tubes

Each ovary is connected to the uterus by
an egg tube. This is sometimes called an oviduct or Fallopian
tube. The egg tube is lined with cilia, which are tiny hairs on
cells. Every month, an egg develops and becomes mature, and is released from an
ovary. The cilia waft the egg along inside the egg tube and into the uterus.

Uterus and cervix

The uterus is also called the womb.
It is a muscular bag with a soft lining. The uterus is where a baby develops
until its birth.

The cervix is a ring of muscle at the
lower end of the uterus. It keeps the baby in place while the woman is
pregnant.

Vagina

The vagina is a muscular tube that
leads from the cervix to the outside of the woman's body. A man's penis goes
into the woman's vagina during sexual intercourse. The opening to the vagina
has folds of skin called labia that meet to form a vulva.
The urethra also opens into the vulva, but it is separate from
the vagina, and is used for passing urine from the body.

The
menstrual cycle

The female reproductive system includes a cycle of
events called the menstrual cycle. It lasts about 28 days, but it
can be slightly less or more than this. The cycle stops while a woman is
pregnant. These are the main features of the menstrual cycle.

The start of the cycle, day 1, is when bleeding from the vagina
begins. This is caused by the loss of the lining of the uterus, with a
little blood. This
is called menstruation or having a period.

By the end of about day 5, the loss of blood stops. The lining of
the uterus begins to re-grow and an egg cell starts to mature in one of
the ovaries.

At about day 14, the mature egg cell is released from the ovary.
This is called ovulation. The egg cell travels through the egg
tube towards the uterus.

If the egg cell does not meet with a sperm cell, the lining of the
uterus begins to break down and the cycle repeats.

If the egg cell meets and joins with a sperm cell, it
is fertilised. It attaches to the lining of the uterus and the
woman becomes pregnant.

The
male reproductive system

The male reproductive system contains these parts:

testes (pronounced
"test-eez")

glands

sperm ducts

urethra

penis.

Testes

The two testes (one of them is called a testis) are
contained in a bag of skin called the scrotum. They have two functions:

to produce millions of male sex cells called sperm

to make male sex hormones, which affect the way a man's body
develops.

Sperm duct and glands

The sperm pass through the sperm ducts,
and mix with fluids produced by the glands. The fluids provide the sperm cells
with nutrients. The mixture of sperm and fluids is called semen.

Penis and urethra

The penis has two functions:

to pass urine out of the man's body

to pass semen into the vagina of a woman during sexual intercourse.

The urethra is the tube inside the
penis that can carry urine or semen. A ring of muscle makes sure that there is
no chance of urine and semen getting mixed up.

Fertilisation
and foetal development

Fertilisation

During sexual intercourse the man's penis releases
semen into the woman's vagina. Sperm cells travel in semen from the penis and
into the top of the vagina. They enter the uterus through the cervix and travel
to the egg tubes. If a sperm cell meets with an egg cell there, fertilisation
can happen. Fertilisation happens when an egg cell meets with a sperm cell and
joins with it.

The fertilised egg divides to form a ball of cells called
an embryo. This attaches to the lining of the uterus and begins to
develop into a foetus(pronounced "fee-tuss") and finally
a baby.

Development of the foetus

The foetus relies upon its mother as it develops.
These are some of the things it needs:

protection

oxygen

nutrients (food and
water).

It also needs its waste substances removing.

The foetus is protected by the uterus and the amniotic
fluid, a liquid contained in a bag called the amnion.

The placenta is responsible for
providing oxygen and nutrients, and removing waste substances. It grows into
the wall of the uterus and is joined to the foetus by the umbilical
cord.

The mother's blood does not mix with
the foetus's blood, but the placenta lets substances pass between the two blood
supplies:

oxygen and nutrients diffuse across the placenta
from the mother to the foetus

waste substances, such as carbon dioxide, diffuse across the
placenta from the foetus to the mother.

Birth

After nine months the baby is ready to be born. The
cervix relaxes and muscles in the wall of the uterus contract, pushing the baby
out of the mother's body.

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